Mobile telephones are becoming smaller and smaller. At some point the keyboard of a mobile telephone, typically a 12-button (alpha-)numeric keyboard commonly known as ITU-T keyboard, will become useless since it becomes too difficult for a user to press keys that are extremely small. Thus, the ITU-T keyboard may become a limiting factor which restricts the design of mobile telephones.
On the other hand, in modern mobile telephones the ITU-T keyboard plays several important roles and acts not only as a dialing keypad for manual entry of telephone numbers to call, but also as an alpha-numeric keyboard for text entry, a game control for arcade games, etc. As regards text entry, each key in the ITU-T keyboard often relates to several characters. A single key may, for instance, relate to the characters “a”, “b” and “c”. Pressing the key once produces the character “a”, pressing the key twice within a short period of time produces the character “b”, and pressing the key three times within a short period of time produces the character “c”. Pressing the button twice slightly more slowly produces two “a”:s. It is rather slow to use a keyboard in such a manner; therefore, various methods for facilitating text entry with an ITU-T keyboard have been developed. An example of such a method, wherein an object is to identify a word entered by a user, is disclosed in U.S. Pat. No. 5,818,437 and is generally known as T9.
Mobile telephones often have a graphical user interface. To facilitate operation of the graphical user interface, mobile telephones often have special navigation key(s), in addition to or integrated with the ITU-T keyboard, such as arrow keys or a combined multi-way navigation key. However, such additional navigation keys add on to the total size of the keyboard, thereby further limiting the freedom to design.
U.S. Pat. No. 6,097,964 discloses a mobile telephone 1 that in addition to an ITU-T keyboard 7 has a roller 10, which replaces traditional navigation key(s) and allows the user to operate the user interface by rotating and depressing the roller to issue commands for browsing and selecting objects in the user interface. The ITU-T keyboard 7 is still used for other purposes like manual dialing and text entry.